METHOD FOR PRODUCING TITANIUM OR TITANIUM ALUMINUM ALLOYS THROUGH TWO-STAGE ALUMINOTHERMIC REDUCTION AND OBTAINING TITANIUM-FREE CRYOLITE AS BYPRODUCTS

Abstract

A method for preparing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts. The method has the following steps: (1) using sodium fluoride and sodium fluotitanate as raw materials, or using sodium fluotitanate as raw materials, and using titanium aluminum alloy powder as a reducing agent; (2) mixing and pressing into pellets, and carrying out first-stage aluminothermic reduction and vacuum distillation; (3) finely grinding after taking out titanium-containing cryolite, mixing with the reducing agent and briquetting, and carrying out second-stage aluminothermic reduction; and (4) separating low-titanium titanium aluminum alloys from high-titanium titanium aluminum alloys, making the low-titanium titanium aluminum alloys and the high-titanium titanium aluminum alloys into powder and returning to the two-stage aluminothermic reduction as the reducing agent; or after the alloys are molten, making the alloys into powder for the two-stage aluminothermic reduction.

Claims

1. A method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts, comprising the following steps: (1) using sodium fluoride and sodium fluotitanate as raw materials, and using aluminum titanium alloy powder obtained through a second-stage aluminothermic reduction as a reducing agent, wherein the reaction formulas of the production proportion of all the materials are shown as follows:
12Na.sub.2TiF.sub.6+(12x+16)Al=12TiAl.sub.x+3Na.sub.3AlF.sub.6+3Na.sub.5Al.sub.3F.sub.14+4AlF.sub.3(1)
and, Ti+xAl=TiAl.sub.x(2); wherein x=0-10; (2) uniformly mixing the raw materials with the reducing agent to obtain a mixture, pressing the mixture into lumps, placing the lumps into a vacuum reduction furnace, heating the placed lumps to 900-1300 C. under a vacuum condition or in an argon atmosphere, and performing a first-stage aluminothermic reduction and vacuum distillation; coagulating a titanium-containing cryolite distilled out on a crystallizer at a low-temperature end of the vacuum reduction furnace, wherein the product mainly comprises Na.sub.3AlF.sub.6, Na.sub.5Al.sub.3F.sub.14, AlF.sub.3 and titanium-containing sub-fluoride, and the residual product in the vacuum reduction furnace is TiAl.sub.x; (3) taking out the titanium-containing cryolite, grinding the titanium-containing cryolite until a particle size is lower than 1.0 mm, using the aluminum powder as the reducing agent, uniformly mixing the grinded titanium-containing cryolite with the aluminum powder to obtain a mixture, and pressing the mixture into lumps, wherein the feeding amount of the aluminum powder follows the rule that the melting point of the AlTi alloys produced by the second-stage aluminothermic reduction is lower than or equal to the temperature of the second-stage aluminothermic reduction temperature; placing the lumps into the reduction furnace, heating the placed lumps to 900-1300 C. in the argon atmosphere and preserving the temperature for 0.5-2 h for the second-stage aluminothermic reduction, wherein according to the products obtained after the reduction reaction is ended and the temperature in the furnace body is reduced to normal temperature, white titanium-free cryolite is formed at upper parts of the products and the aluminum titanium alloys are formed at bottoms of the products, wherein alloys with low content of titanium are formed at the upper parts of the aluminum titanium alloys, which are called as the low-titanium titanium aluminum alloys; the aluminum titanium alloys with comparatively high content of titanium is formed at the lower parts of the aluminum titanium alloys, which are called as the high-titanium aluminum titanium alloys; and (4) dividing or separating the low-titanium aluminum titanium alloys and the high-titanium aluminum titanium alloys with a mechanical division method or a remelting and dumping method of the induction furnace, making the low-titanium aluminum titanium alloys divided out or separated out into powder as the reducing agent of the first-stage aluminothermic reduction, or remelting the aluminum titanium alloy produced by the second-stage aluminothermic reduction to make powder, and returning the powder back to the first-stage aluminothermic reduction as the reducing agent for use.

2. A method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts, comprising the following steps: (1) using sodium fluotitanate as raw materials, and using aluminum titanium alloy powder obtained through a second-stage aluminothermic reduction as a reducing agent, wherein the reaction formulas of the production proportion of all the materials are shown as follows:
3Na.sub.2TiF.sub.6+2NaF+(3x+4)Al=3TiAl.sub.x+Na.sub.3AlF.sub.6+Na.sub.5Al.sub.3F.sub.14(3)
and, Ti+xAl=TiAl.sub.x(4); wherein x=0-10; (2) uniformly mixing the raw materials with the reducing agent to obtain a mixture, pressing the mixture into lumps, placing the lumps into a vacuum reduction furnace, heating the placed lumps to 900-1300 C. under a vacuum condition or in an argon atmosphere, and performing a first-stage aluminothermic reduction and vacuum distillation; coagulating titanium-containing cryolite distilled out on a crystallizer at a low-temperature end of the vacuum reduction furnace, wherein the product comprises the main components of a mixture of Na.sub.3AlF.sub.6, Na.sub.5Al.sub.3F.sub.14, AlF.sub.3 and titanium-containing sub-fluoride, the residual product in the reduction furnace is TiAl.sub.x; (3) taking out the titanium-containing cryolite, grinding the titanium-containing cryolite until the particle size is lower than 1.0 mm, using the aluminum powder as the reducing agent, uniformly mixing the grinded titanium-containing cryolite with the aluminum powder to obtain a mixture, and pressing the mixture into lumps, wherein the feeding amount of the aluminum powder follows the rule that a melting point of the AlTi alloys produced by the second-stage aluminothermic reduction is less than or equal to the temperature of the second-stage aluminothermic reduction; placing the lumps in the reduction furnace, heating the placed lumps to 900-1300 C. in the argon atmosphere and preserving the temperature for 0.5-2 h for the second-stage aluminothermic reduction, wherein according to the products obtained after the reduction reaction is ended and the temperature in the furnace body is reduced to normal temperature, white titanium-free cryolite is formed at upper parts of the products and the aluminum titanium alloys are formed at bottoms of the products, wherein the low-titanium aluminum titanium alloys are formed at the upper parts of the aluminum titanium alloys, which are called as the low-titanium aluminum titanium alloys; the aluminum titanium alloys with comparatively high content of titanium are formed at the lower parts of the aluminum titanium alloys, which are called as the high-titanium titanium aluminum alloys; and (4) dividing or separating the low-titanium aluminum titanium alloys and the high-titanium aluminum titanium alloys with a mechanical division method or a remelting and dumping method of the induction furnace, making the low-titanium aluminum titanium alloys divided out or separated out into powder as the reducing agent of the first-stage aluminothermic reduction, or remelting the aluminum titanium alloys produced by the second-stage aluminothermic reduction to make powder, and returning the powder back to the first-stage aluminothermic reduction as the reducing agent for use.

3. The method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts according to claim 1, wherein, when the first-stage aluminothermic reduction is performed for the first time, metal aluminum powder is used as a reducing agent, and the production proportion of the using dosage of the reducing agent is shown in the reaction formula in step (1).

4. The method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts according to claim 1, wherein, the vacuum distillation lies in that the reduction furnace is vacuumized to 10 Pa or below, and distillation is performed for 1 h or above under the condition that the temperature is 900-1300 C.

5. The method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts according to claim 2, wherein, when the first-stage aluminothermic reduction is performed for the first time, metal aluminum powder is used as a reducing agent, and the production proportion of the using dosage of the reducing agent is shown in the reaction formula in step (1).

6. The method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts according to claim 2, wherein the vacuum distillation lies in that the reduction furnace is vacuumized to 10 Pa or below, and distillation is performed for 1 h or above under the condition that the temperature is 900-1300 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a flow diagram of the method for producing titanium or titanium aluminum alloys by two-stage aluminothermic reduction process and producing titanium-free cryolite as byproducts in the second-stage aluminothermic reduction process, wherein the aluminum titanium alloys produced in the second-stage aluminothermic reduction are remolten and then made into alloy powder, and the alloy powder is used as a reducing agent in the first-stage aluminothermic reduction process;

[0021] FIG. 2 is a flow diagram of the method for producing titanium or titanium aluminum alloys by two-stage aluminothermic reduction process and producing titanium-free cryolite as byproducts in the second-stage aluminothermic reduction process, wherein the aluminum titanium alloys produced in the second-stage aluminothermic reduction are divided into two parts of low-titanium aluminum titanium alloys and high-titanium aluminum titanium alloys, the high-titanium aluminum titanium alloys are sold as commodities, and the low-titanium aluminum titanium alloys are used as the reducing agent in the first-stage aluminothermic reduction process;

[0022] FIG. 3 is an XRD phase analysis diagram of a Ti.sub.3Al alloy product obtained in an embodiment 1 of the present invention;

[0023] FIG. 4 is an XRD phase analysis diagram of titanium-containing cryolite in an embodiment 1 of the present invention;

[0024] FIG. 5 is an XRD phase analysis diagram of a distillation product obtained in an embodiment 2 of the present invention;

[0025] FIG. 6 is an XRD phase analysis diagram of a TiAl3 alloy product obtained in an embodiment 3 of the present invention;

[0026] FIG. 7 is an XRD phase analysis diagram of a TiAl alloy product obtained in an embodiment 5 of the present invention;

[0027] FIG. 8 is an XRD phase analysis diagram of a metal Ti product obtained in an embodiment 7 of the present invention;

[0028] FIG. 9 is an XRD phase analysis diagram of titanium-free cryolite(Na3AlF6) obtained in an embodiment 9 of the present invention;

[0029] FIG. 10 is an SEM (scanning electron microscope) morphology analysis diagram of a layered interface of an aluminum titanium alloy product obtained in an embodiment 9 of the present invention; and

[0030] FIG. 11 is an EDS (energy dispersive spectrum) detection result diagram of the aluminum titanium alloy product obtained in the embodiment 9 of the present invention, wherein an upper diagram and a lower diagram respectively correspond to the position A and the position B of FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0031] XRD phase analysis equipment adopted in an embodiment of the present invention is an X'Pert Pro type X-ray diffractometer.

[0032] SEM morphology analysis equipment adopted in an embodiment of the present invention is an S-4800 type cold field emission scanning electron microscope.

[0033] EDS detection equipment adopted in an embodiment of the present invention is an accessory X-ray energy spectrometer of the S-4800 type scanning electron microscope.

[0034] Metal aluminum powder adopted in an embodiment of the present invention is a product purchased on the market, and the purity of the metal aluminum powder is greater than or equal to 99%.

[0035] Sodium fluoride adopted in an embodiment of the present invention is a powder product purchased on the market, and the purity of the sodium fluoride is greater than or equal to 98%.

[0036] Sodium fluotitanate adopted in an embodiment of the present invention is a powder product purchased on the market, and the purity of the sodium fluotitanate is greater than or equal to 98%.

[0037] A reduction furnace adopted in an embodiment of the present invention is a vacuum reduction furnace with a crystallizer.

Embodiment 1

[0038] 1. Sodium fluoride and sodium fluotitanate are used as raw materials, and 100 g of aluminum titanium alloy powder containing 4.21 wt % of titanium is used as reducing agent; when Ti.sub.3Al alloys (x=1/3 in the formula (1)) are produced, the reaction formulas of the production proportion of all the materials are shown as follows:

3Na.sub.2TiF.sub.6+2NaF+5Al=Ti.sub.3Al+Na.sub.3AlF.sub.6+Na.sub.5Al.sub.3F.sub.14(5)

and, 3Ti+Al=Ti.sub.3Al(6);

[0039] according to the chemical reaction formulas (5) and (6), it can be obtained that 100 g of the reducing agent (aluminum titanium alloy powder) contains 4.21 g of Ti, namely the content of Ti.sub.3Al is 5 g, Al powder participating into the reduction reaction is 95 g, the content of Na.sub.2TiF.sub.6 required by the reaction is 439.11 g, and the content of NaF required by the reaction is 59.11 g; therefore, the actual production materials of the embodiment comprise 439.11 g of Na.sub.2TiF.sub.6, 59.11 g of NaF and 100 g of the aluminum titanium alloy powder containing 4.21 wt % of titanium;

[0040] 2. the production materials are uniformly mixed and then are pressed into lumps, the lumps are placed into a vacuum reduction furnace, the reduction furnace is vacuumized to 10 Pa or below, argon is inflated into the reduction furnace to realize normal pressure, and the reduction furnace is heated to 1100 C. under the argon atmosphere condition, so that a first-stage aluminothermic reduction reaction is completed; and

[0041] 3. after the reduction reaction is ended, the reduction furnace is vacuumized to 10 Pa or below, a product of the reduction reaction is distilled for 2 h under the vacuum condition at the temperature of 1100 C., a distillation product on a crystallizer at the low-temperature end in the vacuum reduction furnace is titanium-containing cryolite, and an alloy product is reserved in a reactor in a loose spongy form; an XRD phase analysis result of the alloy product is shown in FIG. 3, and an XRD phase analysis result of the titanium-containing cryolite is shown in FIG. 4.

Embodiment 2

[0042] 1. Sodium fluotitanate is used as raw materials, and 100 g of titanium aluminum alloy powder containing 4.21 wt % of titanium is used as reducing agent; when the produced product is Ti.sub.3Al alloys (x=1/3 in the formula (3)), the reaction formulas of the production proportion of all the materials are shown as follows:

12Na.sub.2TiF.sub.6+20Al=4Ti.sub.3Al+3Na.sub.3AlF.sub.6+3Na.sub.5Al.sub.3F.sub.14+4AlF.sub.3(7)

and, 3Ti+Al=Ti.sub.3Al(8);

[0043] according to the chemical reaction formulas (7) and (8), it can be obtained that 100 g of the reducing agent (titanium aluminum alloy powder) contains 4.21 g of Ti, namely the content of Ti.sub.3Al is 5 g, Al powder participating into the reduction reaction is 95 g, and the content of Na.sub.2TiF.sub.6 required by the reaction is 439.11 g; therefore, the actual production materials of the embodiment comprise 439.11 g of Na.sub.2TiF.sub.6 and 100 g of the titanium aluminum alloy powder containing 4.21 wt % of titanium;

[0044] 2. the production materials are uniformly mixed and then are pressed into lumps, the lumps are placed into a vacuum reduction furnace, the reduction furnace is vacuumized to 10 Pa or below, and the reduction furnace is heated to 1100 C. under the argon atmosphere condition, so that a first-stage aluminothermic reduction reaction is completed; and

[0045] 3. after the reduction reaction is ended, the reduction furnace is vacuumized to 10 Pa or below, a product of the reduction reaction is distilled for 2 h under the vacuum condition at the temperature of 1100 C., the distillation product on the crystallizer at the low-temperature end in the vacuum reduction furnace is a mixture of the titanium-containing cryolite and aluminium fluoride, and an alloy product is reserved in a reactor in a loose spongy form; an XRD phase analysis result of the alloys is shown in embodiment 1; and an XRD phase analysis result of the distillation product is shown in FIG. 5.

Embodiment 3

[0046] A method in an embodiment 3 is the same as the method in the embodiment 1, but differs from it in that 100 g of aluminum titanium alloy powder containing 1.86 wt % of titanium is used as reducing agent for production of TiAl.sub.3 alloys:

[0047] 1. according to the produced product TiAl.sub.3 (x=3 in the formula (1)), the reaction formulas of the production proportion of all the materials are shown as follows:

3Na.sub.2TiF.sub.6+2NaF+13Al=3TiAl.sub.3+Na.sub.3AlF.sub.6+Na.sub.5Al.sub.3F.sub.14(9)

and, Ti+3Al=TiAl.sub.3(10);

[0048] according to the chemical reaction formulas (9) and (10), it can be obtained that 100 g of the reducing agent (titanium aluminum alloy powder) contains 1.86 g of Ti, namely the content of TiAl.sub.3 is 5 g, Al powder participating in the reduction reaction is 95 g, the content of Na.sub.2TiF.sub.6 required by the reaction is 168.89 g, and the mass of NaF required by the reaction is 22.74 g; therefore, the actual production materials of the embodiment 3 comprise 168.89 g of Na.sub.2TiF.sub.6, 22.74 g of NaF and 100 g of titanium aluminum alloy powder containing 1.86 wt % of titanium;

[0049] 2. all the materials are heated to 1100 C. under the argon atmosphere condition, and the temperature is preserved for 2 h for first-stage aluminothermic reduction; and

[0050] 3. distillation is performed for 2 h at the temperature of 1100 C.; after cooling, the residual metal in a reduction furnace is the TiAl.sub.3 alloys, and an XRD phase analysis result of the TiAl.sub.3 alloys is shown in FIG. 6.

Embodiment 4

[0051] A method in an embodiment 4 is the same as the method in the embodiment 2 and differs from it in that 100 g of aluminum titanium alloy powder containing 1.86 wt % of titanium is used as reducing agent for production of TiAl3 alloys:

[0052] 1. according to the produced product TiAl.sub.3 (x=3 in the formula (3)), the reaction formulas of the production proportion of all the materials are shown as follows:

12Na.sub.2TiF.sub.6+52Al=12TiAl.sub.3+3Na.sub.3AlF.sub.6+3Na.sub.5Al.sub.3F.sub.14+4AlF.sub.3(11)

and, Ti+3Al=TiAl.sub.3(12);

[0053] and therefore, it can be obtained that from the reaction equations (11) and (12) the actual production materials of the embodiment comprise 168.89 g of Na.sub.2TiF.sub.6 and 100 g of aluminum titanium alloy powder containing 1.86 wt % of titanium;

[0054] 2. all the materials are heated to 1100 C. under the argon atmosphere condition, and the temperature is preserved for 2 h for the first-stage aluminothermic reduction; and

[0055] 3. distillation is performed at the temperature of 1100 C. for 2 h; after cooling, the residual metal in a reduction furnace is the TiAl.sub.3 alloys, and an XRD phase analysis result of the TiAl.sub.3 alloys is the same as that in embodiment 3.

Embodiment 5

[0056] A method in an embodiment 5 is the same as the method in the embodiment 1 and differs from it in that 100 g of titanium aluminum alloy powder containing 3.2 wt % of titanium is used as reducing agent for production of TiAl alloys.

[0057] 1. according to the produced product TiAl (x=1 in the formula (1)), the reaction formulas of the production proportion of all the materials are shown as follows:

3Na.sub.2TiF.sub.6+2NaF+7Al=3TiAl+Na.sub.3AlF.sub.6+Na.sub.5Al.sub.3F.sub.14(13)

and, Ti+Al=TiAl(14);

[0058] according to the chemical reaction formulas (13) and (14), it can be obtained that 100 g of the reducing agent (aluminum titanium alloy powder) contains 3.2 g of Ti, namely the content of TiAl is 5 g, Al powder participating in the reduction reaction is 95 g, the content of Na.sub.2TiF.sub.6 required by the reaction is 313.65 g, and the content of NaF required is 42.22 g; therefore, the actual production materials of the embodiment 5 comprise 313.65 g of Na.sub.2TiF.sub.6, 42.22 g of NaF and 100 g of aluminum titanium alloy powder containing 3.2 wt % of titanium;

[0059] 2. all the materials are heated to 1100 C. under the argon atmosphere condition, and the temperature is preserved for 2 h for first-stage aluminothermic reduction; and

[0060] 3. distillation is performed at the temperature of 1100 C. for 2 h; after cooling, the residual metal in the reduction furnace is the TiAl alloys, and an XRD phase analysis result of the TiAl alloys is shown in FIG. 7.

Embodiment 6

[0061] A method in an embodiment 6 is the same as the method in the embodiment 2 and differs from the embodiment 2 in that 100 g of aluminum titanium alloy powder containing 3.2 wt % of titanium is used as reducing agent for production of TiAl alloys.

[0062] 1. according to the produced product TiAl(x=1 in the formula (3)), the reaction formulas of the production proportion of all the materials are shown as follows:

12Na.sub.2TiF.sub.6+28Al=12TiAl+3Na.sub.3AlF.sub.6+3Na.sub.5Al.sub.3F.sub.14+4AlF.sub.3(15)

and, Ti+Al=TiAl(16);

[0063] and therefore, it can be obtained that from the reaction equations (15) and (16) the actual production materials of the embodiment comprise 313.65 g of Na.sub.2TiF.sub.6 and 100 g of the aluminum titanium alloy powder containing 3.2 wt % of titanium;

[0064] 2. all the materials are heated to 1100 C. under the argon atmosphere condition, and the temperature is preserved for 2 h for first-stage aluminothermic reduction; and

[0065] 3. distillation is performed at the temperature of 1100 C. for 2 h; after cooling, the residual metal in a reduction furnace is the TiAl alloys, and an XRD phase analysis result of the TiAl alloys is shown in embodiment 5.

Embodiment 7

[0066] A method in an embodiment 7 is the same as the method in the embodiment 1 and differs from the embodiment 1 in that 100 g of titanium aluminum alloy powder containing 3 wt % of titanium is used as reducing agent for production of pure titanium:

[0067] 1. according to the produced product Ti (x=0 in the formula (1)), the reaction formulas of the production proportion of all the materials are shown as follows:

3Na.sub.2TiF.sub.6+2NaF+4Al=3Ti+Na.sub.3AlF.sub.6+Na.sub.5Al.sub.3F.sub.14(17);

[0068] according to the chemical reaction formula (17), it can be obtained that 100 g of the reducing agent(aluminum titanium alloy powder contains 3 g of Ti), Al powder participating in the reduction reaction is 97 g, the content of Na.sub.2TiF.sub.6 required by the reaction is 560.44 g, and the content of NaF added is 75.44 g; therefore, the actual production materials of the embodiment 7 comprise 560.44 g of Na.sub.2TiF.sub.6, 75.44 g of NaF and 100 g of aluminum titanium alloy powder containing 3 wt % of titanium;

[0069] 2. all the materials are heated to 1100 C. under the argon atmosphere condition, and the temperature is preserved for 2 h for first-stage aluminothermic reduction; and

[0070] 3. distillation is performed at the temperature of 1100 C. for 2 h; after cooling, the residual metal in the reduction furnace is the Ti, and an XRD phase analysis result of the Ti is shown in FIG. 8.

Embodiment 8

[0071] A method in an embodiment 8 is the same as the method in the embodiment 2 and differs from the embodiment 2 in that 100 g of aluminum titanium alloy powder containing 3 wt % of titanium is used as reducing agent for production of pure titanium:

[0072] 1. according to the produced product Ti (x=0 in the formula (3)), the reaction formulas of the production proportion of all the materials are shown as follows:

12Na.sub.2TiF.sub.6+16Al=12Ti+3Na.sub.3AlF.sub.6+3Na.sub.5Al.sub.3F.sub.14+4AlF.sub.3(18);

[0073] It can be obtained through the chemical reaction formula (18), the actual production materials of the embodiment comprise 560.44 g of Na.sub.2TiF.sub.6 and 100 g of the aluminum titanium alloy powder containing 3 wt % of titanium;

[0074] 2. all the materials are heated to 1100 C. under the argon atmosphere condition, and the temperature is preserved for 2 h for first-stage aluminothermic reduction; and

[0075] 3. distillation is performed at the temperature of 1100 C. for 2 h; after cooling, the residual metal in the reduction furnace is the metal Ti, and an XRD phase analysis result of the Ti is shown in embodiment 7.

Embodiment 9

[0076] A method in an embodiment 9 is the same as the method in the embodiment 1 and differs from the embodiment 1 in that 100 g of aluminum titanium alloy powder containing 2.13 wt % of titanium is used as reducing agent for production of titanium aluminum alloys containing 42.55% of titanium.

[0077] 1. The titanium aluminum alloys containing 42.55 wt % of titanium are the same as the product TiAl.sub.2.4 alloys (x=2.4 in the formula (1)), and therefore, the reaction formulas of the production proportion of all the materials in the embodiment 9 are shown as follows:

3Na.sub.2TiF.sub.6+2NaF+11.2Al=3TiAl.sub.2.4+Na.sub.3AlF.sub.6+Na.sub.5Al.sub.3F.sub.14(19)

And Ti+2.4Al=TiAl.sub.2.4(20)

[0078] according to the chemical reaction formulas (19) and (20), it can be obtained that 100 g of the reducing agent (aluminum titanium alloy powder) contains 2.13 g of Ti, namely the content of TiAl.sub.2.4 is 5 g, Al powder participating in the reduction reaction is 95 g, the content of Na.sub.2TiF.sub.6 required by the reaction is 196.03 g, and the mass of NaF added is 26.39 g; therefore, the actual production materials of the embodiment 9 comprise 196.03 g of Na.sub.2TiF.sub.6, 26.39 g of NaF and 100 g of aluminum titanium alloy powder containing 2.13 wt % of titanium;

[0079] 2. all the materials are heated to 1100 C. under the argon atmosphere condition, and the temperature is preserved for 2 h for first-stage aluminothermic reduction; and

[0080] 3. distillation is performed for 2 h at the temperature of 1100 C.; after cooling, the residual metal in a reduction furnace is the TiAl.sub.2.4 alloys, and an chemical component analysis result of the TiAl.sub.2.4 alloys is shown in Table 1.

TABLE-US-00001 TABLE 1 Chemical components Al Ti Ca Si Fe Percentage by 57.4963 42.0368 0.0537 0.0152 0.0044 mass (%)

Embodiment 10

[0081] Titanium-free cryolite and aluminum titanium alloys are produced through vacuum reduction by using the titanium-containing cryolite distilled out through the first-stage aluminothermic reduction in the embodiment 7 as a raw material and aluminum powder as reducing agent.

[0082] 1. after the first-stage aluminothermic reduction process, 427.78 g of the titanium-containing cryolite is grinded until the particle size is lower than 1.0 mm, wherein the content of titanium is 12.84 g; 100 g of aluminum powder is used as reducing agent; the grinded titanium-containing cryolite and the aluminum powder are uniformly mixed and then are pressed into lumps; the lumps are placed into the vacuum reduction furnace, the vacuum reduction furnace is vacuumized to 10 Pa or below, argon is inflated into the vacuum reduction furnace to normal pressure, the lumps are heated to 1200 C. under the argon atmosphere condition, and the temperature is preserved for 2 h for the second-stage aluminothermic reduction; and

[0083] 2. after the materials in the reduction furnace are cooled to normal temperature, a product is taken out and separated out, so as to obtain the white titanium-free cryolite and the aluminum titanium alloys with the forming amounts of 414.94 g and 112.84 g respectively in theory; the aluminum titanium alloys can be used as reducing agent for the next first-stage aluminothermic reduction process to produce metal titanium, and the cycle continues; an XRD phase analysis result of the white titanium-free cryolite is shown in FIG. 9, and an XRF component analysis result is listed in Table 2;

TABLE-US-00002 TABLE 2 Chemical components F Na Al Mg Ca Si Fe K Ti Percentage by 59.8487 22.7601 16.6017 0.7133 0.0254 0.0177 0.0058 0.0043 <0.001 mass(%)

[0084] It can be seen from Table 2 that the cryolite produced in the embodiment 10 completely conforms with the national standard GB/T 4291-1999 cryolite and can be directly applied in the aluminum electrolysis industry. Low-titanium aluminum titanium alloys are formed at the upper layer of the aluminum titanium alloy product, and high-titanium aluminum titanium alloys are formed at the lower layer of the aluminum titanium alloy product. An SEM image and an energy spectrum analysis result of the aluminum titanium alloy product are respectively shown in FIG. 10 and FIG. 11.

[0085] The titanium-containing cryolite obtained in the first-stage aluminothermic reduction of the embodiments 1-9 can be further treated by the method shown in the embodiment 10, the aluminum powder is adopted for performing the second-stage vacuum aluminothermic reduction, the obtained white titanium-free cryolite can be applied in the aluminum electrolysis industry, and the aluminum titanium alloys can fully returns to the next first-stage aluminothermic reduction process as the reducing agent.